Concentrating solar power (CSP) plants produce electricity without any pollutant emission, which is one of the most attractive alternatives to fossil fuels. The thermal energy storage (TES) benefits CSP plants to produce electricity during temporary weather transients and peak-load demand hours. However, the main drawback of the CSP plants is the high investment costs. To improve the economic viability, it is necessary to design CSP plants appropriately. In this study, an optimal co-allocation model of solar field and TES for CSP plants considering with the operation demand of power system is developed to deal with the tradeoff between investment costs and benefits. To consider realistic operating constraints account for the interaction between hourly variability, the uncertainties of solar irradiation and wind power are characterised by a set of scenarios. In addition, the large number of scenarios is reduced to relieve the computational burden. The validity of the proposed model is demonstrated by case study results.